Gaseous electric discharge device



July 10, 1934. T. E. FOULKE 1,965,586

GASEOUS ELECTRIC DISCHARGE DEVICE Filed Jan. 1931 Patented July 1 0, 1 934 l v d l I f 1,965,586 GASEOUS ELECTRIC DISCHARGE pEvIcE- Ted E. Foulke, Nut ley, N. J assignor to General Electric Vapor Lamp Company, Hoboken, N. 1., a corporation of New Jersey Application January 6, 1931, Serial No. 506,849 9 Claims. (Cl- 176-126) The present invention relates to electric gaseglow supporting surface not only have a lower ous discharge devices, and particularly to light work function than that of .the particles comprisemitting discharge devices of the cathode glow ing the surface from which the glow is to be extype eluded, but also have an appreciably greater 5 A particular object of the invention is to proaffinity for each other than they have for the vide a gaseous dis harge device in which the particles comprising the latter surface, the glow cathode glow is confined to predetermined areas is confined to the desired area throughout-the on the electrode surface. Another object of the useful life of the device. This logically follows, invention is to provide a discharge device having since the discharge will take place to the surface 10 a uni-directional light emission characteristic. of lower work function, asis well known, and 65 Another object of the invention is to provide 9. even if particles having the lower work function device which will operate on either A. C. or D. C. r putt r d ont h su f o h h r work without appreciable change in the direction of function, they will sputter off again so rapidly light emission. A further object of the inventhat no appreciable glow discharge can take place tion is to provide a discharge device in which the to the latter surface. It is obvious, of course, 70 heat radiation in the direction of light emission from the above that I do not find it necessary isminimized. Still another object of the invenuse a substance such as mica, q r, and the tion is to provide a discharge devicewhich will like. on the surfa e from whi h th low is o be have a long useful life. Other objects andadexcluded, such as has been heretofore unsuccessvantages of my invention will appear from the fu y attempted. In fact, ,when a coating of 7 following detailed description of embodiments barium intermixed with the oxide thereof is emthereof, or from an inspection of the accompany- P y for the e upp t ng surface, the i d i most satisfactory substance which I have found The invention consists in an electric gaseous for-use on the surface from which the glow is to discharge device having the several new and nov 1 be excluded is aluminum or aluminum oxide. 80

features hereinafter set forth and claimed. Antimony. selenium and copp Oxide are exam- For many purposes it is highly desirable to con ples of other metals or oxides thereof which simifine the negative, or cathode, glow to predeterlarly confine the glow to the barium coated surmined areas of an electrode surface, as is eviface, and ca be used. if desired. in P a e Of the denced by the numerous efforts of previous inelectrically conducting aluminum or the electri- 5 vestigators to achieve this lt, Of th varicallyinsulating oxide thereof in the manufacture ous expedients suggested heretofore, however, all of devices such as low voltage lamps. As a result have been extremely limited in utility, or else f my new inv n i n itis im now mm i l y resulted either in lamps which only temporarily feasible for the first/time to produce a gaseous as had the desired characteristic, or in lamps which discharge device hav t w co fi d t any 90 were so complicated and difficult to manufacture desired area onan electrode surface, that they were prohibitively expensive. For ex- My inv nt i sp cially useful in pr d n ample, it has been proposed heretofore to coat discharge devices for use in signs, in inspection that portion of an electrode from which it was Work, and the like Where light from only One 40 desired to exclude the glow discharge with an indirection can be utilized, S nc y Constructing 95 sulating substance such as mica or a lacquer, a discharge device with flat electrodes arranged Experience has taught, however, that the glow in substantially the Same plane, with the back rapidly crept over such a surface, due to the proof said electrodes coated according to my invenduction of a conducting film thereon, either by tion, a light source having a uni-directional light the sputtering of conducting particles onto said emission characteristic on either A. C. or D. C. surface in the area contiguous to the glow supis obtained, eliminating substantialiyall the reporting surface of the electrode, or by the reducflection losses heretofore suffered with other types tion of the insulating substance, or by both of of artificial light sources. Furthermore, by suitthese phenomena. Hence the coatings heretofore ably treating the face of the electrodes the glow proposed have been found to be impractical and may be caused to present a legend within each 1 have not had any commercial use. I have now discharge device, if desired, this legend remaindiscovered, however, that the desired result may ing clear and unblurred throughout the life of be readily attained by a novel construction of my the device. invention. This new structureis based upon my In some cases, as in the inspection of articles discovery that if the particles comprising the where a close temperature control is necessary,

it is essential that a minimum of radiant heat trodes are preferably turned downward in a 90 should be directed toward the work. My new are having a radius of a few millimeters since discharge device is especially suitable for such it has been found that this eliminates the exuse, since at least half of the heat therefrom is cessive blackening of the bulb 1 adjacent to the 5 normally radiated from the back of the elecedges of said electrodes which is encountered trodes, while by mixing a small amount of carbon when said edges are directed toward the adjacent or the like with the aluminum coatin as by walls of said bulb. For operation on 110 volt using a carbonaceous binder which is later recircuits, A. C. or D. 0., it is desirable to produce a du y heating, even a greater proportion of coating 5 having a relatively low work function the heat may be a d n a d ec o away on the face of the electrodes 4, to which it is del as the back of the electrodes s un bs ucted y may be any of the alkali or alkaline earth metals insulating bodies or the like, the heat is freely or compounds thereof, and may be produced in radiated therefrom, so that the electrode runsat any of th usual ways, but I prefer a coating of a lower mp a ure than it would if so 'cbbarium or strontium, or the like, intermixed 9 s'tructed.

The useful life of gaseous discharge devices of producing such a. coating, as fully set forth in my the cathode glow type is, of course, limited for all copending application, Serial N 0. 381,425, filed p a ti al purp s y the bla k n n of the en- July 27, 1929, includes the steps of coating the VelOpe 0f e d I have found a this front surface of the electrodes with a compound blackening is almost entirely due to metal D such as barium or strontium carbonate, or with a ter d fr m th ed r ha p corners of th elecmixture thereof, a suitable carbonaceous binder Wall. As a re ult a discharge device With sufficient to reduce said compounds to the oxide, 0( P n r electr de such as is described abo the oxide then being further reduced by means an envelope of practical diameter for commerface A surface so r ar d has a eXtre eIy al p p s the l t d necessarily approach low work function, as compared to the nickel or y o y t the glass Walls- 1 have discovered, other metal normally used for the electrode, with howev r, hat hi sputtering m y be almost the result that the cathode glow is temporarily ircly limin t d by r llin r ni h edges confined to the coated surface. It has been found, of the electrodes in such a manner that said elechuwever, th t; n ntinued o e tion th 1 -1- ro do n present a sharp edge comer umor other coating metalgradually creeps, prob- 35 to the adjacent wall of the envelope. When so ably by a sputtering process, r d nto th constructed my n w discharge device has been uncoated back surface of the electrode, so that found to have a ex m long useful i after a considerable period the entire electrode t For purposes of illustration I have shown a dissupports t glow To n t t creeping charge device co p i a preferred emb9diof the cathode glow I coat the back of the elec- 40 meht of my invention, with variohs modlflcahohs trodes with a substance having a higher work re f. n he a ompanyin drawing, in whic function than that of the glow supporting suris an eleveticnal View 0f a gaseous i face, and which at the same time has an apprecharge device constructed according to my ciably lower affinity for particles of the glow sup- Venticnporting surface than said particles have for each 45 2 is a sectional View of the same devlcer other, so that particles of said glow supporting taken on the line 2-2 of Fig. 1,

Fig. 3 is an elevational View Of a gaseous dlS- tan e quickly putter off again preventing the charge device showing. an alternative electrode formation f a sputtered oating of any amnecis uc able density on said substance. Finely powdered 50 Fl'g- 4 is a sechohal Vlew of the devlce of aluminum is preferably used for this purpose, estaken at the line thereflfr r pecially where the active surface consists of the Fi 5 is an elevational Vlew of a modification aforesaid mixture of barium and barium oxide of the device of f since it has been found to be extremely effective, Fi 6 i a sectional view taken at 1he line but any other substance which has the like pro- 55 of and perty of resisting this creeping of the cathode Figs. 7 and 8 are plan views of an electrode glow Such as antimony, selenium, osmium or assem y such as shown in with the glow sulating materials like aluminum oxide and copconfined to predetermined areas thereof to per oxide, may be used if desired. A carbonaceous sent the binder such as nitrocellulose dissolved in amyl 60 with Particular reference Figs- 1 2 acetate or other suitable solvent is preferably emconventional envelopel of glass or other suitable played amx the aluminum or other substance material, within whish is a suitable gaseous to the electrode surface. This coating, which is ing, such as neon, hshum or othehgases Vapors applied at the same stage of manufacture as the mixtures thereof Preferably wlth y small barium carbonate, is of course heated during the 65 percentage of $011, at a Pressure of 15-60 treatment of the device to a temperature sufliof me c y hes a pair of leads 2 and 3 sealed cient to reduce the binder to carbon, which re- ,thereinto in the usual manner, said leads sup- ,mains intermixed t t aluminum This porting at their inner ends the two similar eleebon somewhat blackens the back of each elec trodes 4 which are Welded thereto. Sa d e ctrode, making it a better heat emitter than the 70 trodes 4, which are preferably formed of sheet front thereof, with the result that considerably nickel h like, are -c rcular in shape and more than half the heat from said electrodes is are arranged in a plane which is transverse to the radiated from the back thereof. major axis of the envelope 1 with the straight In Figs. 3 and 4 there is shown a similar enedges of said electrodes parallel and about 9. milvelope l, with inleads 2 and 3. Said leads supfl; limeter apart. The circular edges of these elecport the rectangular electrodes 10, a vitreous bead 11 lending rigidity to the assembly. Said electrodes 10 are arranged in a plane which is-parallel with the axis of the envelope 1 with'theadjacent edges thereof parallel and about i a millimeter apart. The edges of said electrodes 10 which are adjacent to the walls of the envelope 1 are rolled over in an arc of approximately 180 having a radius of say 1 or 2 m. m. so of will not be directed toward said walls. The ends of said electrodes 10 may also be rolled over in like manner if it is desired to reduce sputtering therefrom. Said electrodes 10 are coated on both front and back in the same manner as the electrodes 4, and a simil employed. With this emitted toward the side of the construction the light is envelope 1, instead of toward the end, as in the structure of Figs.

1 and 2.

In the modification of the structure of Figs. 1 and 2 which is shown in Figs. 5 and 6 the elecformed as quadrants of a hollow sphere, so arranged as to jointly present a hemispherical toward the end of the bulb 1. With this construction, which gives a slightly different light distribution which is desirable in certain cases, it is unnecessary to turn the edges of the electrodes, since the edges already extend in the desired direction. In all other respects this modification is identical with the structure of Figs. land 2. v

In Figs. 7 and 8 the principle of my invention is shown as employed to confine the cathode glow to predetermined areas of the face of the electrodes 4 of a structure such as illustrated in-Figs. and 2. InFig. "I the dotted area 5 has a coating of low work function, while the back of said electrodes and the area within the letter A on the face thereof are coated with the aluminum paint. In operation the letter A remains dark against the bright background provided by the remainder of the electrode. The structure of Fig. 8 is identical save that here the letter area has the coating of low work function 5 while the background is coated with aluminum, with the result that the letter appears bright against a dark background. In either case the delineation of the letter or other legend remains unimpaired throughout a long useful life, due to the effect of the aluminum in resisting any creeping of the glow. 1

With each of the above constructions it is apparent that the light will have a uni-directional characteristic which will remain substantially unchanged during operation on either A. C. or D. C. circuits. Due to the novel configuration of the electrodes the excessive sputtering onto those portions of the envelope 1 through which light is to be transmitted, which would normally be encountered with such an arrangement of the electrodes, is avoided, the devices therefore having a long useful life.

While my invention has been described by reference to certain embodiments thereof, it is to be understood that it is not limited thereto, and that various omissions, substitutions, and changes may be made in the structure described, within the scope of the appended claims without departing from the spirit of my invention.

I claim as my invention:

1. An electric gaseous discharge device comprising a sealed envelope having a gaseous atmosphere therein, and metal electrodes sealed into said envelope, at least one of said electrodes ed with an alkaline having a portion thereof coa that the edges thereprising a trodes sealed into said envelope,

activating substance of low work function, and another portion of said electrode coated with a metallic material having a lower affinity for particles of said coating of low work function than said particles have for each other, whereby the -*discharge is confined to the alkaline coated portions of said electrode throughout device.

2. An electric gaseous discharge device comprising a sealed envelope having a gaseous atmosphere therein, and metal electrodes sealed into said envelope, a portion of the surface of at least one of said electrodes being coated with an alkaline substance having a low work function while another portion of said surface is coated with aluminum.

3. An electric gaseous discharge device comprising a sealed envelope having a gaseous atmosphere therein, and electrodes sealed into said envelope, a portion of the surface of at least one of said electrodes consisting of an alkaline substance having alow work function while another portion of said surface consists of aluminum oxide.

4. An electric gaseous discharge device comprising a sealed envelope having a gaseous atmosphere therein, and electrodes sealed into said envelope, at least one of said electrodes'having a portion thereof coated with an alkaline metal intermixed with the oxide thereof, and another portion of said electrode coated with to which particles sputtered from said alkaline coating do not readily adhere.

5. An electric gaseous discharge device comprising a sealed envelope having a gaseous atmosphere therein, and electrodes sealed into said envelope, a portion of the surface of at least one of said electrodes consisting of an alkaline metal intermixed with the oxide thereof 'while another portion of said surface consists of aluminum.

6. An electric gaseous discharge device comsealed envelope having a gaseous atmosphere therein, electrodes sealed into said envelope, a coating of a substance having a low work function on the face of at least one of said electrodes, and a coating of particles sputtered from said first mentioned coating do not readily adhere on the back of said electrode, said material having a black substance intermixed therewith.

'1. An electric gaseous discharge device comprising a sealed envelope having a gaseousatmosphere therein, electrodes sealed into said envelope, a coating of an alkaline metal on face of at least one -of said electrodes, and a coating of aluminum on the back of said electrode, said aluminum being intermixed with carbon to increase the heat radiation therefrom.

8. In an electric gaseous discharge device, in combination, a sealed envelope, a gaseous atmosphere therein, and substantially plane electhe edges'of said electrodes presenting a rounded contour to the nearest portion of said envelope, said edges being out of contact with any insulating medium.

9. An electric gaseous discharge device comprising a sealedenvelope having a. gaseous atmosphere therein, and metal electrodes sealed into said envelope, a portion of the surface of at least one of said electrodes being coated with an alkaline substance having a low work function while another portion of said surface is coated with finely divided aluminum.

the life, of said a material 1 a material to which the 

